The study was carried out on thale cress, or Arabidopsis as it’s known scientifically, which is closely related to broccoli, kale, mustard greens, and other siblings of the brassica family and is popular for science experiments. It is commonly used in experiments because it was the first plant to have its genome sequenced, and scientists are intimately familiar with how it works.

Going forward with the question of whether a plant knows it’s being eaten, the University of Missouri researchers first took a precise audio recording of the vibrations a caterpillar makes as it eats the thale cress leaves, with the working theory that plants could feel or hear the vibrations in some way.

The researchers controlled the experiment by coming up with other vibrations that simulated other natural vibrations like wind noise that the plant might encounter.

The results? According to Modern Farmer, the thale cress produces mustard oils that are mildly toxic when eaten and sends them throughout its leaves to try to keep the predators away. The research also revealed that when the plants felt or heard “munching vibrations” from the caterpillar, they sent out extra mustard oils. But the plants didn’t react when other vibrations were present.

“However, our work is the first example of how plants respond to an ecologically relevant vibration. We found that feeding vibrations signal changes in the plant cells’ metabolism, creating more defensive chemicals that can repel attacks from caterpillars.”